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// Same as rustc's `tests/ui/async-await/async-closures/captures.rs`, keep in sync
#![feature(async_trait_bounds)]
use std::future::Future;
use std::pin::pin;
use std::task::*;
pub fn block_on<T>(fut: impl Future<Output = T>) -> T {
let mut fut = pin!(fut);
let ctx = &mut Context::from_waker(Waker::noop());
loop {
match fut.as_mut().poll(ctx) {
Poll::Pending => {}
Poll::Ready(t) => break t,
}
}
}
fn main() {
block_on(async_main());
}
async fn call<T>(f: &impl async Fn() -> T) -> T {
f().await
}
async fn call_once<T>(f: impl async FnOnce() -> T) -> T {
f().await
}
#[derive(Debug)]
#[allow(unused)]
struct Hello(i32);
async fn async_main() {
// Capture something by-ref
{
let x = Hello(0);
let c = async || {
println!("{x:?}");
};
call(&c).await;
call_once(c).await;
let x = &Hello(1);
let c = async || {
println!("{x:?}");
};
call(&c).await;
call_once(c).await;
}
// Capture something and consume it (force to `AsyncFnOnce`)
{
let x = Hello(2);
let c = async || {
println!("{x:?}");
drop(x);
};
call_once(c).await;
}
// Capture something with `move`, don't consume it
{
let x = Hello(3);
let c = async move || {
println!("{x:?}");
};
call(&c).await;
call_once(c).await;
let x = &Hello(4);
let c = async move || {
println!("{x:?}");
};
call(&c).await;
call_once(c).await;
}
// Capture something with `move`, also consume it (so `AsyncFnOnce`)
{
let x = Hello(5);
let c = async move || {
println!("{x:?}");
drop(x);
};
call_once(c).await;
}
fn force_fnonce<T>(f: impl async FnOnce() -> T) -> impl async FnOnce() -> T {
f
}
// Capture something with `move`, but infer to `AsyncFnOnce`
{
let x = Hello(6);
let c = force_fnonce(async move || {
println!("{x:?}");
});
call_once(c).await;
let x = &Hello(7);
let c = force_fnonce(async move || {
println!("{x:?}");
});
call_once(c).await;
}
// Capture something by-ref, but infer to `AsyncFnOnce`
{
let x = Hello(8);
let c = force_fnonce(async || {
println!("{x:?}");
});
call_once(c).await;
let x = &Hello(9);
let c = force_fnonce(async || {
println!("{x:?}");
});
call_once(c).await;
}
}
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